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  1. #1
    mathew stouffer's Avatar
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    Default Exhaust vent length

    Is there a limit and or slope requirement for bathroom exhaust fan vents. This one went from the second floor bathroom down above the master bedroom and terminated under the soffit.

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  2. #2
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    Default Re: Exhaust vent length

    Quote Originally Posted by mathew stouffer View Post
    Is there a limit and or slope requirement for bathroom exhaust fan vents. This one went from the second floor bathroom down above the master bedroom and terminated under the soffit.

    I am sure there is, but at least that one goes down hill. The air duct from it is not properly supported, neither is that flexible duct. The flexible duct is also being crushed between the top plate and the roof sheathing.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  3. #3
    A.D. Miller's Avatar
    A.D. Miller Guest

    Default Re: Exhaust vent length

    Quote Originally Posted by mathew stouffer View Post
    Is there a limit and or slope requirement for bathroom exhaust fan vents. This one went from the second floor bathroom down above the master bedroom and terminated under the soffit.
    Mathew:

    bathroom fan

    http://www.nutone.com/PDF/Specifications/695spec.pdf - See page 2.


  4. #4
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    Default Re: Exhaust vent length

    Quote Originally Posted by A.D. Miller View Post

    That Nutone chart is based on 10 foot duct sections, which indicates it might be for rigid duct?

    If it is, that flexible air duct will be much worse off than shown in the chart.

    Matthew,

    Contact the manufacturer (Nutone at 888-336-6151 Technical Support) (Broan at 800-637-1453 Technical Support), they may want you to send those photos to them via e-mail. Do you have an idea of the length of that duct? They will ask you for that, I am sure.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  5. #5
    A.D. Miller's Avatar
    A.D. Miller Guest

    Default Re: Exhaust vent length

    Quote Originally Posted by Jerry Peck View Post
    That Nutone chart is based on 10 foot duct sections, which indicates it might be for rigid duct?

    If it is, that flexible air duct will be much worse off than shown in the chart.

    Matthew,

    Contact the manufacturer (Nutone at 888-336-6151 Technical Support) (Broan at 800-637-1453 Technical Support), they may want you to send those photos to them via e-mail. Do you have an idea of the length of that duct? They will ask you for that, I am sure.
    JP: Most contractors here install minimally sized fans based solely on the use of rigid duct and then install flex duct 30-40 feet in ever-widening loops across the attics. I write them all up and put the burden of proof of compliance on them.


  6. #6
    jim young's Avatar
    jim young Guest

    Default Re: Exhaust vent length

    Quote Originally Posted by mathew stouffer View Post
    Is there a limit and or slope requirement for bathroom exhaust fan vents. This one went from the second floor bathroom down above the master bedroom and terminated under the soffit.

    Terminated under the sofit? which code? 2006 IRC?


  7. #7
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    Default Re: Exhaust vent length

    Quote Originally Posted by jim young View Post
    Terminated under the sofit? which code? 2006 IRC?
    Jim,

    I think you are going in this direction with your questions.

    From the 2006 IRC. (underlining is mine)
    - M1506.2 Recirculation of air.
    Exhaust air from bathrooms and toilet rooms shall not be recirculated within a residence or to another dwelling unit and shall be exhausted directly to the outdoors. Exhaust air from bathrooms and toilet rooms shall not discharge into an attic, crawl space or other areas inside the building.

    The bathroom exhaust discharge termination is allowed under the soffit as Matthew said it was, however, no soffit vents are allowed near it ... otherwise the discharge will effectively be recirculated back into the attic.

    Is that where your questions were heading?



    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  8. #8
    mathew stouffer's Avatar
    mathew stouffer Guest

    Default Re: Exhaust vent length

    It was ~ 20 feet. The builder is going to reroute the vent. Thanks guys.


  9. #9
    jim young's Avatar
    jim young Guest

    Default Re: Exhaust vent length

    Quote Originally Posted by Jerry Peck View Post
    Jim,

    I think you are going in this direction with your questions.

    From the 2006 IRC. (underlining is mine)
    - M1506.2 Recirculation of air.
    Exhaust air from bathrooms and toilet rooms shall not be recirculated within a residence or to another dwelling unit and shall be exhausted directly to the outdoors. Exhaust air from bathrooms and toilet rooms shall not discharge into an attic, crawl space or other areas inside the building.

    The bathroom exhaust discharge termination is allowed under the soffit as Matthew said it was, however, no soffit vents are allowed near it ... otherwise the discharge will effectively be recirculated back into the attic.

    Is that where your questions were heading?

    Yes now how many builders don't put sofit vents around the whole under side?


  10. #10
    A.D. Miller's Avatar
    A.D. Miller Guest

    Default Re: Exhaust vent length

    Quote Originally Posted by jim young View Post
    Yes now how many builders don't put sofit vents around the whole under side?
    Jim: The manufacturers require that the ducts terminate in one of the following: (1) Dampered roof caps, (2) Dampered soffit caps, or (3) Dampered wall caps.

    Most in my area terminate them: (1) In the attic, (2) Under a roof vent, or (3) in the soffit. All are wrong and I write all of them up as such.


  11. #11
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    Default Re: Exhaust vent length

    Quote Originally Posted by A.D. Miller View Post
    Jim: The manufacturers require that the ducts terminate in one of the following: (1) Dampered roof caps, (2) Dampered soffit caps, or (3) Dampered wall caps.

    Aaron,

    Do you have an example of such an installation instruction? There is a so-so damper (being kind) at the exhaust fan, just wondering if they also require a damper at the termination as I don't recall seeing any installation instructions which did.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  12. #12
    A.D. Miller's Avatar
    A.D. Miller Guest

    Default Re: Exhaust vent length

    Quote Originally Posted by Jerry Peck View Post
    Aaron,

    Do you have an example of such an installation instruction? There is a so-so damper (being kind) at the exhaust fan, just wondering if they also require a damper at the termination as I don't recall seeing any installation instructions which did.
    JP: From the document I posted earlier:

    • Discharge is through 3" round duct through roof or wall.

    From one of their fan installation instructions:

    Ductwork
    1. Use 4" round duct.
    2. Plan to run duct from discharge opening of fan to the
    outside. For best fan performance, make the duct run as
    short as possible and use a minimum number of elbows.
    3. Use optional ducting accessories as required.

    From the horse's mouth:

    Mr. Miller

    Below is the reply from our technical support department:

    You are correct that the Broan units must completely exit the structure to the outdoors at dampered terminuses.

    I have some links below to Deflect-o Corporation’s Soffit Vent Kit accessories that they offer, which we do not.

    Maybe something like the Deflect-o unit would help your builder.

    http://www.deflecto.com/OMS/tier2_template_air.aspx?ProductID=1357

    http://www.deflecto.com/OMS/getimage.aspx?ID=4161

    http://www.deflecto.com/OMS/getimage.aspx?ID=2528


    Sorry for the delay in answering your inquiry.

    I do hope this information is helpful. Technical can be reached at 1-800-637-1453 if you need further assistance.

    Tammy
    Broan-NuTone LLC
    Broan Customer Service
    1-800-558-1711
    webinfo@broan.com






  13. #13
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    Default Re: Exhaust vent length

    The only thing which remotely mentions dampered discharges terminations is his note to you "dampered terminuses", other than than, nothing says it.

    Your main problem, as I read it, was that the builders were terminating the duct inside the attic/soffit, probably with no termination other than laying over a soffit vent.

    I thought that everyone knew, by this century, that was no allowed. Guess not.

    But as for requiring a "dampered terminuses"? Not sure that one reference in that one letter would work. If you have had luck with it, go for it, at least it gets the duct through the roof/wall/soffit.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  14. #14
    Ralph Smith's Avatar
    Ralph Smith Guest

    Default Re: Exhaust vent length

    It appears the vent goes down, then back up over the insulated flex duct and out the soffitt. If so, moisture will condense and water will build until the vent connector releases from somewhere and water spills onto the sheetrock. From that day forward the fan will vent into the attic. In the northern climates it is recommended that insulated duct be used to slow the condensation.


  15. #15
    Ed Voytovich's Avatar
    Ed Voytovich Guest

    Default Re: Exhaust vent length

    It is perfectly possible and even perhaps likely that the installer can screw up even a short run. Assuming there are no crimps or "traps" in the flexible duct, the best way to determine whether it delivers something close to the rated CFM is to use a flow hood and a digital instrument to measure both pressure and flow. (energyconservatory.com)

    Nobody expects home inspectors to have this gear.

    Our tests suggest that going from the 3 or 4" discharge on the fan to a 6" insulated duct through the nearest way out (roof, gable end, soffit, code inspector, your first wife) and terminating in a 6" roof/wall/soffit cap gives the best performance.

    Just an FYI.


  16. #16
    A.D. Miller's Avatar
    A.D. Miller Guest

    Default Re: Exhaust vent length

    Quote Originally Posted by Jerry Peck View Post
    The only thing which remotely mentions dampered discharges terminations is his note to you "dampered terminuses", other than than, nothing says it.

    Your main problem, as I read it, was that the builders were terminating the duct inside the attic/soffit, probably with no termination other than laying over a soffit vent.

    I thought that everyone knew, by this century, that was no allowed. Guess not.

    But as for requiring a "dampered terminuses"? Not sure that one reference in that one letter would work. If you have had luck with it, go for it, at least it gets the duct through the roof/wall/soffit.
    JP: Let me preface this comment with the fact that I like you. Now that we have the niceties behind us, you are being completely unreasonable. The people told you that they wanted dampers on the termini of the ducts and then sent you links to pictures of those devices. It could not be clearer.

    OK, it could be clearer, but it's not. And, I think it is clear enough to do the trick. In the perfect world, which we all know only exists in the northern climes of Flahdah, they would say that "the duct MUST be terminated OUTSIDE of the building at a DAMPERED wall, roof, or eaves cap. FAILURE TO FOLLOW THESE INSTALLATION INSTRUCTIONS PRECISELY WILL RESULT IN IMMEDIATE DECAPITATION, WITH PREJUDICE!"


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